Rapid exchange delivery system for self-expanding stent

ABSTRACT

A catheter assembly is provided having an inner member and an outer member extending along a longitudinal axis, the inner member and the outer member having a coaxial configuration and dimensioned for relative axial movement. The outer member has a wall defining an opening such as a longitudinal slot; an expanding member such as a leaf spring is connected to the inner member, the leaf spring being adapted to engage with the longitudinal slot so as to maintain rotational alignment between inner member and outer member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of Ser. No. 09/919,490 filed Jul. 31,2001 now U.S. Pat. No. 6,679,909, which is assigned to the same Assigneeas the present application.

BACKGROUND OF THE INVENTION

The invention relates to stent delivery systems, which are used toimplant a stent into a patient's body lumen to maintain the patencythereof. The stent delivery system is useful in the treatment and repairof body lumens, including coronary arteries, renal arteries, carotidarteries, and other body lumens.

Stents are generally cylindrically-shaped devices which function to holdopen and sometimes expand a segment of a blood vessel or other bodylumen. They are particularly suitable for use to support and hold back adissected arterial lining which can occlude the fluid passagewaytherethrough. Stents also are useful in maintaining the patency of abody lumen, such as a coronary artery, after a percutaneous transluminalcoronary angioplasty (PTCA) procedure or an atherectomy procedure toopen a stenosed area of the artery.

Typically, a stent is delivered intraluminally through a percutaneousincision through the femoral or renal arteries. The stent is mounted onthe distal end of an elongated catheter and the catheter and stent areadvanced intraluminally to the site where the stent is to be implanted.A variety of devices are known in the art for use as stents and haveincluded coiled wires in a variety of patterns that are expanded afterbeing placed intraluminally. Three different approaches for expandingstents have been developed in the art, namely, balloon expanded stents,elastically self-expanding stents, and heat expanded stents. Balloonexpanded stents are placed over a deflated balloon mounted on thecatheter. The balloon is then inflated to expand the stent radiallyoutwardly into contact with the arterial wall, whereupon the stentundergoes plastic deformation and remains in an expanded state to holdopen and support the artery. Elastically self-expanding stents areadapted to be delivered in an elastically compressed state whileconfined within an outer restraining sheath, but to elastically expandwhen the sheath is removed and to provide support to the vessel withinwhich it is implanted. Heat expanded stents are made from heat-sensitivematerials such as nickel-titanium, are cooled in a compressed shapebefore insertion into the patient, but assume a pre-existing expandedshape when exposed to the body temperature of a patient.

With respect to self-expanding stents, typically a retractable sheath ispositioned over the self-expanding stent which is mounted on the distalend of the catheter. Once the catheter has been advanced intraluminallyto the site where the stent is to be implanted, the sheath is withdrawnthereby allowing the self-expanding stent to expand radially outwardlyinto contact with the arterial wall, thereby holding open and supportingthe artery. Both balloon expanded stents and heat sensitiveself-expanding stents may also be delivered within a retractable sheath,similar to that used with a self-expanding stent. In such cases thesheath may function to secure the stent on the catheter during insertionor to prevent sharp edges of the stent from tearing at the wall of thelumen during insertion.

One embodiment of a catheter delivery system is the so-called“over-the-wire” delivery system, in which a catheter is introduced intothe patient over a guide wire which has been previously introduced. Inthis embodiment, the guide wire runs within a lumen extending the entirelength of the catheter. Another embodiment of the catheter deliverysystem is the so-called “rapid exchange” delivery system, in which theguide wire runs within a lumen in the catheter extending from the distaltip of the catheter to a point just proximal of where the stent ispositioned on the catheter, at which point the lumen terminates on theoutside of the catheter and the guide wire emerges from the catheter toextend proximally, outside of the catheter. Thus, the catheter of a“rapid exchange” delivery system has a guide wire lumen port at thedistal end of the catheter, and a proximal port spaced a relativelyshort distance from the distal end and a relatively long distance fromthe proximal end of the catheter. This “rapid exchange” configurationallows the surgeon to rapidly and single-handedly place the deliverysystem over the guide wire or to exchange one delivery system foranother, because the length of the guide wire lumen in the catheter ismuch shorter than used in an over-the-wire delivery system.

One of the problems associated with the prior art catheter-deliverysystems which use a retractable outer sheath is that the addition of aretractable sheath tends to reduce the overall flexibility of thedelivery system. Another problem is that, in the case of the rapidexchange delivery system, the addition of a retractable sheath tosurround the catheter introduces a problem of rotational alignmentbetween the sheath and the catheter. Upon commencement of installing thedelivery system over the guide wire, the surgeon must introduce theproximal tip of the guide wire into the catheter lumen at the distal tipof the catheter. The surgeon then advances the guide wire proximallythrough the catheter lumen until the proximal tip of the guide wireemerges from the catheter and protrudes through an opening in the wallof the sheath. If, during the foregoing process, the sheath rotatesrelative to the catheter, the surgeon may have difficulty in aligningthe opening with the guide wire tip, so as to get the guide wire tip toprotrude from the opening. This complication can be a major problem forthe surgeon to resolve under the pressure of surgery.

Thus, there has been found in the art a need for a reliablerapid-exchange stent delivery system for a self expanding stent, inwhich rotational alignment between the outer sheath and the catheter maybe maintained prior to and during the process of positioning thedelivery system over the guide wire. Further, the art has found a needfor a delivery system for a self expanding stent which has improvedflexibility characteristics. The present invention addresses these andother needs.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter delivery system havingimproved flexibility characteristics. In a further aspect, the inventionis directed to a rapid-exchange catheter delivery system having an outersheath, in which the sheath is held in rotational alignment with thecatheter prior to and during the process of positioning the deliverysystem over a guide wire. Means for maintaining such rotationalalignment may assume the form of a leaf-spring or other expanding memberattached to the catheter and adapted to protrude through a slot oropening defined in the sheath.

A catheter assembly for removably attaching an intravascular stent isprovided in which an elongated catheter has an inner member and an outermember extending along a longitudinal axis, wherein the inner member andthe outer member have a coaxial configuration and are dimensioned forrelative axial movement. A self-expanding stent, having an open latticestructure, and being adapted to be expandable to an open configuration,is mounted on the inner member, within the outer member.

The present invention includes a leaf spring, attached to the innermember, which engages with a slot on the outer member so as to maintainthe inner member and the outer member in rotational alignment. The leafspring is adapted to deflect radially inwardly and to disengage from theslot in the outer member, either after the distal tip of a guide wire isextended from within the outer member over the leaf-spring outwardlythrough the slot in the outer member, or when the outer member isproximally withdrawn relative to the inner member.

In a further aspect of the invention, the distal end of the inner memberis configured as a helical coil to enhance the overall flexibility ofthe delivery assembly.

The invention also includes a method of implanting a self-expandingstent utilizing the catheter-delivery system described above. Using thecatheter-delivery system, a guide wire is proximally advanced through alumen of the delivery system from the distal end until it encounters theleaf-spring, whereupon the guide wire is deflected outwards through theslot. The leaf spring is deflected radially inwardly and disengages fromthe slot in the outer member when the outer member is proximallywithdrawn relative to the inner member.

The invention also relates to a method of assembling the delivery systemdescribed above. The method includes inserting the ends of the leafspring through the wall of a tubular sleeve so that the ends arepositioned within the lumen and the center portion of the leaf-spring ispositioned outside the lumen of the sleeve. The sleeve is then slid overthe inner member to a desired position on the inner member. The sleevemay be attached by friction fit, adhesive, or laser welding.

Other features and advantages of the present invention will become moreapparent from the following detailed description of the invention, whentaken in conjunction with the accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a stent delivery system embodying featuresof the present invention.

FIG. 1 a is a detail view of an aspect of FIG. 1, showing an embodimentof how the leaf-spring mechanism may be positioned relative to the innermember.

FIGS. 2 a, 2 b and 2 c are sectional views exemplifying embodiments ofthe leaf-spring mechanism embodying features of the present invention.

FIG. 3 is a perspective view of an aspect of the stent delivery systemof FIG. 1.

FIGS. 4 through 6 exemplify the stages of deploying a stent within abody lumen using a delivery system made in accordance with the presentinvention.

FIG. 7 is a perspective view of an aspect of a stent delivery systemexemplified in FIG. 1.

FIG. 8 is a perspective view of an aspect of the stent delivery systemexemplified in FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to a rapid exchange delivery cathetersystem in which a stent is delivered intraluminally into a humanpatient's body lumen, such as a coronary artery, carotid artery, renalartery, peripheral artery and veins, and the like. The inventionprovides for a stent delivery catheter assembly, a method of assembly,and a method of use in which a stent is implanted in a patient. In oneaspect, the invention is directed to a rapid-exchange catheter deliverysystem having an outer sheath, in which the sheath is held in rotationalalignment with the catheter prior to and during the process ofpositioning the delivery system over a guide wire. Means for maintainingsuch rotational alignment may assume the form of a leaf-spring or otherexpanding member attached to the catheter and adapted to protrudethrough a slot or opening defined in the sheath.

There are numerous prior art stent delivery systems which may be used inconjunction with the present invention. The stent delivery systemssuitable for use with the present invention are “rapid exchange”delivery systems which have an outer sheath adapted to slide over aninner sheath so as to cover a stent. The invention described in detailherein is described in the context of an elastically self-expandingstent delivery system. However, the invention is not limited to suchuse, and may equally be used with a delivery system for a balloonexpanded stent or heat expanded stent.

In one embodiment of the invention, as exemplified in FIG. 1, a rapidexchange catheter assembly 20 is provided to deliver and implant astent. Rapid exchange catheters are known in the art and details of theconstruction and examples of use are set forth in U.S. Pat. Nos.5,458,613; 5,346,505; and 5,300,085. Rapid exchange catheter assembly 20incorporates an inner member 22 and an outer member 24 arranged incoaxial alignment. Inner member 22 is slidably positioned within outermember 24 and relative axial movement between the two members isprovided by inner member control handle 26 and outer member controlhandle 28. The control handles 26, 28 can take numerous forms, but aredepicted schematically for ease of illustration. As an example, however,control handles 26, 28 can take the form of a thumb-switch arrangement,a rotating-screw-type arrangement, or a ratcheting arrangement. Suchcontrol handle means are well known in prior art catheter-deliverysystems.

Inner member 22 has a proximal end 30 and a distal end 32. Inner membercomprises a catheter 34 which has proximal end 36 and distal end 38. Thecatheter 34 may be surrounded by a first jacket 35, adapted to lendlubricity to the inner member. Inner member further comprises a guidewire lumen 40, having proximal end 42 and distal end 44. As exemplifiedin FIG. 1, guide wire lumen 40 is configured to extend distally, fromits proximal end 42 which is positioned adjacent to catheter 34 and justproximal of the distal end 38 thereof, to its distal end 44 which islocated at the distal end 32 of the inner member. The profile of theguide wire lumen 40 extends distally along and adjacent the catheter 34,and then deflects from being adjacent to the catheter so as to extendcoaxially therewith. Guide wire lumen 40 terminates in a distal opening45 at its distal end 44.

Inner member 22 further includes a helical coil 46 having a proximal end48 and a distal end 50. The helical coil may be positioned surroundingthe guide wire lumen 40 at a location on the guide wire lumen where itextends coaxially with the catheter 34. As exemplified in FIG. 3, thehelical coil 46 may be connected to the catheter 34 by means of flexiblearms 52 which extend from the coil to a ring 54 surrounding the catheter34 and crimped onto the catheter. Preferably, the helical coil, arms,and rings may be laser cut from a single tubular metallic structure. Thearms are adapted to transfer axial force from the catheter 34 to thehelical coil 46. It will be appreciated that the helical coil 46provides a degree of stiffness to the inner member at a position wherethere is no catheter, while at the same time providing adequateflexibility.

With continued reference to FIG. 1, inner member 22 further comprises adistal tip 56 which surrounds the guide wire lumen 40 at the distal end32 of the inner member, and is shaped to provide a low profileatraumatic end so as to facilitate movement of the delivery systemthrough the patient's vasculature. A flexible protective layer 58 maycover the distal tip. A self expanding stent 60 in compressed state maybe positioned about the distal tip 52, held in place by outer member 24.A blocking element 62 adapted to prevent proximal movement of the stent60 relative to inner member 22 may be positioned between the distal tip56 and the helical coil 46, and may also be adapted to act as aradio-opaque marker. In an alternative embodiment, the helical coil mayextend all the way to the distal end 32 of the inner member, with thedistal tip 56 adapted to accommodate the coil. A second protectivejacket 63 may surround the coil 46, the guide wire lumen 40, and portionof the catheter 34, as exemplified in FIG. 1.

The outer member 24 is configured to surround the inner member 22, andmay have a diameter at its distal end larger than at its proximal end inorder to accommodate all the elements of the inner member. Theself-expanding stent 60 in its compressed state is positioned around thedistal tip 56 of the inner member 22 and is held in compressed state bythe outer member 24. As exemplified in FIGS. 4-6, when the outer memberis withdrawn proximally relative to the inner member, the stent 60 ispermitted to assume its expanded state so as to support the body lumenwithin which it is implanted.

A further component of the inner member 22 is an expanding member suchas a leaf spring 64. In one embodiment the leaf-spring may be attachedto the catheter 34 via a cylindrical sleeve 66 adapted to fit onto thecatheter at a position proximal of the proximal end 42 of the guide wirelumen 40. For purposes of assembly, the leaf-spring may be firstattached to the cylindrical sleeve 66 by inserting the ends of theleaf-spring through the wall of the sleeve so that the central portionof the leaf-spring is positioned on the outside of the sleeve lumenwhile the ends of the leaf-spring are positioned within the sleevelumen, as exemplified in FIG. 1 a. The resulting combination may then beslid longitudinally over the catheter 34 to the desired position, asexemplified in FIG. 1. The sleeve may be fixed to the inner membereither by adhesive, by heat welding, or by laser welding. Alternatively,the sleeve may be heated prior to sliding it over the inner member, sothat, when cooled, a friction fit to the inner member is achieved. Oncethe leaf-spring 64 is fixed to the inner member, it is adapted toprotrude into an opening such as a slot 68 formed in the wall of theouter member 24. In a further aspect, the leaf spring may also protrudebeyond the slot so that a substantial portion of the leaf spring ispositioned outside the outer member. It will be appreciated that whenthe leaf-spring protrudes into the slot it provides rotational alignmentbetween the outer member and the inner member. By maintaining suchrotational alignment, the ease with which a guide wire may be threadedthrough the delivery system 20 is greatly enhanced, as is explained morefully below. In one particular embodiment, the leaf-spring may be madeof a material having highly elastic properties such as a nickel-titaniumalloy including Nitinol, or a chromium-cobalt-nickel alloy includingElgiloy™ (manufactured and sold by Elgiloy of Elgin, Ill.), which willnot readily lose its shape through plastic deformation should it besubjected to large strain. This quality is useful in that it has beenfound that, during assembly or storage of the delivery catheter 20, theleaf-spring 64 may be accidentally subjected to strains which mightplastically deform or fracture a leaf-spring of similar proportions madeof stainless steel.

In one embodiment, outer member 24 may be modified in that the perimeterof the slot 68 in the outer member may be reinforced by adding thereto acollar 69 formed of the same material as the outer member, so that thethickness of the outer member along the longitudinal edges of the slotis greater than the overall average thickness of the outer member. Thecollar may be connected to the outer member by adhesive or known heat orlaser welding techniques. It will be appreciated that the ability of theoutside catheter to resist bending is reduced in the vicinity of theslot, and thus accidental excessive bending at the location of the slotmay cause the outer member to plastically deform and form a permanentkink along a longitudinal edge of the slot, which may render thedelivery assembly unusable. Thus, reinforcement of the outer member inthe vicinity of the slot as described above may reduce accidental damageof such kind. The slot itself may be cut into the outer member and thecollar with a sharp edge, or, alternatively, by known means using laser.

With reference to FIGS. 4-6, preparation for deploying a stent within apatient (not shown) using the delivery assembly of the present inventionmay commence using procedures which are well-known in the art, with thepositioning of a guide wire 70 in the vasculature of the patient, afterwhich the proximal tip (not shown) of the guide wire is left protrudingfrom the patient. The proximal tip is then inserted in the distalopening 45 of the distal end 44 of the guide wire lumen 40 and threadedthrough the guide wire lumen until the proximal tip emerges from theproximal end 42 of the lumen. When the proximal tip of the guide wire isfurther advanced proximally from the proximal end 42 of the guide wirelumen, it may first contact the leaf-spring 64 and then deflectoutwardly to emerge from the slot 68 in the outer member 24. It will beappreciated that within the catheter 20 there is a passageway for aguide wire extending between the distal opening 45 of the guide wirelumen 40 to the opening or slot 68. While the short cross section of theleaf-spring may be generally rectangular (FIG. 2 a), in order tofacilitate outward deflection of the guide wire the short crosssectional profile of the leaf-spring may depart from a rectangularshape, and may either have a generally “U” shape or a generally “V”shape as exemplified in FIGS. 2 b and 2 c. The leaf-spring may beadapted to remain engaged within the slot after the guide wire isadvanced through the slot, as exemplified in FIG. 4, but to disengage ata later stage, as set forth below. The delivery system 20 is thenadvanced over the guide wire and its distal portion is inserted into thepatient as required. In order to implant the self-expanding stent 60,the guide wire 70 is positioned in a patient's body lumen, at vesselwall 72, and typically guide wire 70 extends past a stenosed region 74.The catheter 20 is advanced along the guide wire until the stent 60 ispositioned within stenosed region 74.

As exemplified in FIGS. 5 and 6, self-expanding stent 60 is implanted instenosed region 74 by moving outer member 24 in a proximal direction,either while simultaneously moving inner member 22 in a distal directionor while holding it stationary relative to the patient. The leaf-spring64 may be adapted to disengage from the slot when the outer member ismoved proximally over the inner member, in that the outer member maydepress the leaf-spring and, also, the outer member itself may slightlydeform so as to pass over the leaf-spring. As portions of self-expandingstent 60 are no longer contained by outer member 24, the stent willexpand radially outwardly into contact with the vessel wall 72 in thearea of stenosed region 74. When fully deployed and implanted, as shownin FIG. 6, the stent 60 will support and hold open the stenosed region74 so that blood flow is not restricted. It will be appreciated that,after the leaf-spring is disengaged from the slot and during proximalmovement of the outer member 24 relative to inner member 22, theleaf-spring 64 represents no appreciable resistance to the movement ofthe outer member 24, as the leaf-spring is no longer engaged in the slot68 of the outer member but may slide against the inner wall of the outermember. After stent 60 is implanted and contacts stenosed region 74, thecatheter 20 and guide wire 70 are withdrawn from the patient's vascularsystem.

The stent as described herein can be formed from any number ofmaterials, including metals, metal alloys and polymeric materials.Preferably, the stent may be formed from metal alloys such as stainlesssteel, tantalum, or the so-called heat sensitive metal alloys such asnickel titanium (NiTi). Stents formed from stainless steel or similaralloys typically are designed, such as in a helical coil or the like, sothat they are spring biased outwardly.

With respect to all of the embodiments disclosed above, inner member 22and outer member 24 can be formed from polymeric materials includingpolyurethanes, polyethylenes, polyethylterpthalate, and nylons.Similarly, sleeve 66 can be formed from polyurethane, elastomericpolyesters and the like. Generally speaking, the more proximal portionsof inner member 22 and outer member 24 will be formed of a polymericmaterial that is stiffer than the distal section so that the proximalsection has sufficient pushability to advance through the patient'svascular system. On the other hand, the more distal portion of innermember 22 and outer member 24 can be formed of a more flexible materialso that the distal portion of the catheter will remain flexible andtrack more easily over the guide wire.

Other modifications and improvements may be made without departing fromthe scope of the invention. For example, the leaf spring is not limitedto the shape exemplified in the drawings, but may be any expandingmember and may assume any shape which expands to protrude through anopening or slot in the outer member. Accordingly, it is not intendedthat the invention be limited, except as by the appended claims.

1. A catheter assembly comprising: a stent; an elongated catheter havingan inner member and an outer member extending along a longitudinal axis,the inner member and the outer member having a coaxial configuration anddimensioned for relative axial movement, and wherein the outer memberhas a wall defining an opening; and an expanding member connected to theinner member and being adapted to engage with the opening so as tomaintain rotational alignment between inner member and outer member, theinner member including a distal portion having the stent mounted thereonand the outer member being adapted to at least partially cover the stentand retractable to uncover the stent.
 2. The catheter assembly of claim1 wherein the expanding member has opposing ends, further comprising atubular sleeve defining a lumen, the ends of the expanding member beingpositioned within the sleeve lumen and the sleeve being positionedexternally around and coaxially aligned with the inner member.
 3. Thecatheter assembly of claim 1 wherein the expanding member is adapted toflexibly deform sufficiently to disengage from the opening and allowrelative axial movement between inner member and outer member.
 4. Thecatheter assembly of claim 1 wherein the expanding member is made of anickel-titanium alloy.
 5. The catheter assembly of claim 1 wherein theouter member has a wall, the thickness of the wall adjacent the edges ofthe opening being greater than the average thickness of the wall overthe length of the outer member.
 6. A catheter assembly comprising: a. acatheter having i. a proximal end and a distal end; ii. a distal openingat the distal end; iii. a proximal opening spaced a relatively shortdistance from the distal end and a relatively long distance from theproximal end; iv. a passageway for a guide wire extending between thedistal opening and the proximal opening; v. an inner member and an outermember extending along a longitudinal axis, the inner member and theouter member having a coaxial configuration and dimensioned for relativeaxial movement, the inner member including a distal portion adapted toreceive a medical device and the outer member being adapted to at leastpartially cover the medical device and retractable to uncover themedical device, wherein the outer member has a wall defining theproximal opening; and vi. an expanding member connected to the innermember and being adapted to engage with the proximal opening so as tomaintain rotational alignment between inner member and outer member. 7.The catheter assembly of claim 6 wherein the passageway is adapted toreceive a guide wire inserted into the passageway, and to direct an endof the guide wire onto the expanding member.
 8. The catheter assembly ofclaim 7 wherein the expanding member is adapted to deflect the end ofthe inserted guide wire through the proximal opening.
 9. The catheterassembly of claim 6 wherein the outer member is adapted to deform theexpanding member when the outer member is moved axially in relation tothe inner member.
 10. The catheter assembly of claim 6 wherein theexpanding member is adapted in relation to the outer member to disengagefrom the proximal opening when the outer member is moved axially inrelation to the inner member.
 11. The catheter assembly of claim 6wherein the expanding member has opposing ends, further comprising atubular sleeve defining a lumen, the ends of the expanding member beingpositioned within the sleeve lumen and the sleeve being positionedexternally around and coaxially aligned with the inner member.
 12. Thecatheter assembly of claim 6 wherein the expanding member is adapted toflexibly deform sufficiently to disengage from the proximal port andallow relative axial movement between inner member and outer member. 13.The catheter assembly of claim 6 herein the expanding member is made ofa nickel-titanium alloy.
 14. The catheter assembly of claim 6 herein theexpanding member is made of a chromium-cobalt-nickel alloy.
 15. Acatheter assembly comprising: an elongated catheter having an innermember and an outer member extending along a longitudinal axis, theinner member and the outer member having a coaxial configuration anddimensioned for relative axial movement, and wherein the outer memberhas a wall defining a longitudinal slot; and a leaf spring connected tothe inner member and being adapted to engage with the longitudinal slotso as to maintain rotational alignment between inner member and outermember, the inner member including a distal portion adapted to receive amedical device and the outer member being adapted to at least partiallycover the medical device and retractable to uncover the medical device.16. The catheter assembly of claim 15 wherein the leaf-spring hasopposing ends, further comprising a tubular sleeve defining a lumen, theends of the leaf-spring being positioned within the sleeve lumen and thesleeve being positioned externally around and coaxially aligned with theinner member.
 17. The catheter assembly of claim 15 wherein theleaf-spring is adapted to flexibly deform sufficiently to disengage fromthe slot and allow relative axial movement between inner member andouter member.
 18. The catheter assembly of claim 15 wherein theleaf-spring is made of a nickel-titanium alloy.
 19. The catheterassembly of claim 15 wherein the leaf-spring is made of achromium-cobalt-nickel alloy.